1. Field of the Invention
This invention relates to integrated circuit (IC) packaging technology, and more particularly, to a heat-dissipating device for use in an integrated circuit package for heat dissipation.
2. Description of Related Art
An integrated circuit package is used to enclose one or more semiconductor chips therein for easy handling and utilization. During operation of the semiconductor chips, however, electricity will cause the semiconductor chips to produce heat. If the heat is not effectively dissipated, it can cause damage to the internal circuitry or electronic components of the semiconductor chips. Therefore, there is a need for providing internal heat-dissipating means in the integrated circuit package for heat dissipation during operation. Conventionally, this can be achieved by embedding a heat sink or a heat block within integrated circuit package, or by directing a stream of cooled air or liquid against the semiconductor chips. When using a heat sink or a heat block, it is required to expose a part of the heat sink or heat block to the outside of the encapsulant for enclosing the semiconductor chip so that the heat can be dissipated to the atmosphere or another externally linked heat-dissipating means. In design, it is desired to increase the exposed area to the atmosphere and shorten the heat-conducting path from the heat-generating source to the exposed area for the purpose of increasing the heat-dissipating efficiency.
One drawback to the use of heat sink or heat block, however, is that, since such heat-dissipating devices are molded through stamping, the edges there of would be undesirably rolled over, which would cause the encapsulating resin used in the molding process to flash through these rounded corners to the exposed area of the heat-dissipating device and thereby covers a considerable part of the exposed area of the heat-dissipating device. This would degrade the heat-dissipating efficiency. Moreover, the flashed resin would cause the exposed area of the heat-dissipating device to lose planarity, making the heat-dissipating device unable to be linked securely to the external heat-dissipating means. The flashed resin can be removed through sanding or laser polishing, but such post-treatment would undesirably increase the overall manufacture cost and may easily cause surface damage to the integrated circuit package.
FIG. 6 is a schematic sectional diagram of an integrated circuit package incorporating a conventional heat-dissipating device. As shown, the heat-dissipating device 16 is a molded piece of a heat-conductive material, having a top side exposed to the outside of the encapsulant 17. Further, the heat-dissipating device 16 is formed with a cutaway part 16a at the edge thereof. During the molding process, the cutaway part 16a can help prevent the melted encapsulation resin from flashing onto the exposed surface of the heat-dissipating device 16. When the melted resin enters the cutaway part 16a, it would be increased in viscosity and thus reduced in flowability so that it would hardly flash. One drawback to this heat-dissipating device 16, however, is that the cutaway part 16a is flat and narrow, which would nevertheless allow a small but considerable part of the melted resin to flash onto the exposed surface of the heat-dissipating device 16.
One solution to the foregoing problem is depicted in FIG. 7. As shown, in this heat-dissipating device, a metal layer 31 of silver or platinum is coated over the cutaway part 16a. The flashed encapsulation resin adheres to this metal layer 31 with a less strength than to the heat-dissipating device 16; and therefore, the flashed resin over the exposed surface of the heat-dissipating device 16, if any, can be easily removable during post-treatment. One drawback to this solution, however, is that the coating of the metal layer 31 over the cutaway part 16a of the heat-dissipating device 16 would make the overall manufacture process more complex, and thus would undesirably increase the manufacture cost. In addition, it would not prevent the flashing of the encapsulation resin over the exposed surface of the heat-dissipating device 16.